This invention relates to safety release pins for use with apparatus such as fire extinguishers and the like for preventing such apparatus from being operated until the pin is removed and for providing a visual indication as to whether or not the apparatus has been previously operated.
In U.S. Pat. No. 3,814,298 issued on June 4, 1974 to Arne Hansen, there is disclosed a safety release pin for use with apparatus such as a fire extinguisher, an insecticide sprayer and the like in which fluid or powder is confined and dispensed under pressure. The safety release pin is used to prevent accidental operation of the apparatus in that the release pin must be removed before the apparatus can be operated.
The release pin comprises a ring at one end and a locking structure at the other. The locking structure includes a pair of arms extending in a parallel spaced relationship, each having an outwardly projecting tab defining a cam surface. As the pin is inserted through openings in the fire extinguisher handle, the cam surfaces engage the peripheral edge of the openings, flexing the arms toward one another. After the tabs clear the openings in the fire extinguisher handle, the arms spring back to their locking position. When it is desired to use the fire extinguisher, the pin is pulled by the ring and fracture occurs at a weakened section of the arms at the rearward edge at least one of the cam surfaces, the tab breaks off at the weakened section of the arm. If both tabs break off, and if the pin is then inadvertently reinserted into the fire extinguisher handle, the lack of tabs on the pin will indicate that the apparatus has previously been operated.
In this safety release pin, the breaking mode for the tab is pure tension. Accordingly, only a small cross-sectional area can be used in the weakened section of the arms due to force breakaway limitations prescribed by Underwriters Laboratories for safety release pins of this type. Such constraint makes the arms vulnerable to breakage during normal handling.
Moreover, in some instances, only one of the two arms may break off as the pin is removed. With one arm intact, the pin could be inadvertently reinserted into the handle of the fire extinguisher and the remaining arm could conceal the fact that tampering or previous use has occurred.